At present it appears that only the group owner can message a group via Private Messaging.

I'd like to specify to change this behaviour for one or more groups, so that any group member can message the group.

I'm conscious of privacy/spam though, so perhaps this could be tied in with a user setting for "don't email me"?

This would be useful - It should also be a Group Admin decision - ie. can group members send PMs to the group...